<?php

//生成验证码图片 
 
srand((double)microtime()*1000000); 
$im = imagecreate(62,20); 
$black = ImageColorAllocate($im, 0,0,0); 
$white = ImageColorAllocate($im, 255,255,255); 
$gray = ImageColorAllocate($im, 200,200,200); 
imagefill($im,68,30,$gray); 
while(($authnum=rand()%100000)<10000);
//将四位整数验证码绘入图片 
session_start();
$_SESSION['authcode'] = md5($authnum);
imagestring($im, 5, 5, 2, $authnum, $white); 
for($i=0;$i<200;$i++)   //加入干扰象素 
{ 
    $randcolor = ImageColorallocate($im,rand(0,255),rand(0,255),rand(0,255));
    imagesetpixel($im, rand()%70 , rand()%30 , $randcolor); 
}
Header("Content-type: image/PNG");  
ImagePNG($im); 
ImageDestroy($im); 

?>